Directional radio system



Dec. 3, 1946. M. LEEDS DIRECTIONAL RAYD IO SYSTEM 5' Sheets-Sheet 1 Filed Sept. 15, 1941 Figl.

li'a nsmit fer- Invent 01":- Laurance M. Leeds,

' Rece/i er 1 b'borney.

' His 4 Dec.3, 1946. L. M. LEEDS DIRECTIONAL RADIO SYSTEM Filed Sept. 15,- 1941 5 Sheets-Sheet 2 Pi g .9.

IIIIII/III/II/III/I/l/fi/I/III/M/II/IIII/II/IIIIIIIIIIIIIIIIIIII/IIIIII/IIIL Invento e ed s, atjmi Laurance M. L by His Attorney.

Dec. 23,1946. L. M; LEEDS 2,412,159

7 DIRECTIONAL RADIO SYSTEM I Filed Sept. 15, 1941 5 sh eets sheet x l 462 Z? a; 30 eceiver I I I l/r "1 7- 45' H E 40 3 an mitt s Inventor;

Lagudance M. Leeds, by M17 His Attorney.

Dec. 3, 1946. L. M. LEEDS DIRECITIONAL RADIO SYSTEM Filed Sept. 15, 1941 s Sheets- Sheet 4 7Fansmitter- Invent or: Lagrance M. Leeds by H His 2t Dec. 3, 1945. L M, LEEDS 2,412,159

I DIRECTIONAL RADIO SYSTEM I Filed Sept. 15, 1941 5 Sheets-Sheet 5 Fig.5.

Receiver 7Fdnsmitter Inventor: Laurance M. Leeds,

ttor ney.

Patented Dec. 3, 1946 ZAlZJSd DHRECTIONAL RADIO SYSTEM Laurance M. Leeds, Rotterdam Junction, N. Y.,

assignor to General Electric Company, a corporation of New York Application September 15, 1941, Serial No. 410,836

13 Claims. (01. 250-11) My invention relates to directional radio systems and it has for one of its objects to provide new and improved means whereby the directivity of such systems may be altered or controlled.

In directive radio systems such as are employed for the location of the moving objects, such as air or water craft, it is highly important that the directivity of the system be readily and rapidly variable by electrical means. In this way, a remote area, for example, in which a moving object is located may be rapidly scanned by variation of the directivity of the system thereby to observe the movements of the remote object in the area. This may be effected without movement of the antenna itself. Of course, as the observed craft moves from the scanned area to other areas, the antenna structure involved may be physically moved to direct it to the new area which may then be electrically scanned to observe the movements of the body in the new area.

Such apparatus requires the use of an antenna mattress mounted physically for orientation both in elevation and in azimuth, or train. My invention has for its object to provide in connection with such a system, improved means whereby the directivity of the mattress may be electricall varied in order that a remote area to which the antenna mattress is physically directed may be electrically scanned.

A further object of m invention is to provide such means by which the directivity of the pattern may be varied without movement, or me.- chanical alteration, of any physical structure on the mattress.

A further object of my invention is to provide such a system adapted for impulse transmission and for reception of impulses resulting from reflection of the transmitted impulses from remote reflecting surfaces and in which the directivity of the system is varied for both transmission and reception.

The novel features which I believe to be characteristic of my invention are set forth with par ticularity in the appended claims. My invention, itself, however, both as to its organization and method of operation, together with further ohjects and advantages thereof may best be understood by reference to the following descrip tion taken in connection with the accompanying drawings, in which Fig. 1 represents an embodiment of my invention; Fig. 2 represents. in

6 and '7 represent capacitance switches of the type employed in connection with the form of the invention shown in Fig. 1; Fig. 8 represents a capacitance switch of the form employed in the form of the invention shown in Fig. 4; and Fig. 9 represeints the structure of the diode employed in the invention.

Referring to Fig. l of the drawings, I have illustrated therein four antenna elements l, 2, 3 and 4. Each of these elements comprises four dipoles arranged in pairs, each dipole having a length equal to a half wave length of the wave at which it operates; the dipoles of each pair being arranged end to end, and the pairs being spaced apart in parallel relation by a distance equal to half of the wave length of the wave at which the antenna operates. All of these antenna elements I, 2, 3 and 4 are arranged in a single plane upon an antenna mattress such as that shown at 5 in Fig. 2. This mattress may be supported in any convenient way as by means of the support 6 for orientation in a horizontal plane, or azimuth, and the antenna mattress 5 is arranged for rotation about the horizontal pivot l for orientation in the vertical plane, or in elevation.

While the antenna elements I and 2 are arranged directly end to end and the antenna elements 3 and are arranged end to end, the elements 3 and 4 being spaced by half a wave length from the elements I and 2, the proportions of this space relationship have been departed from in Fig. 1 for purposes of clarification of the drawings.

Energy to be radiated by the antenna elements I, 2, 3 and 4 may be supplied from a transmitter 8 through a transmission line 9, which extends to a point it and which is there divided into four branches H, l2, l3 and It each leading to a respective antenna element thereby to transmit energy from the transmitter to the different antenna elements. While each of these lines comprises an outer shield preferably cylindrical and which is grounded throughout its length, and an inner conductor, to simplify the drawings, the outer shield is shown only fragmentarily. This is true with respect to all of the concentric conductors shown in the drawings.

Each of the antenna elements has feedpoint terminals indicated at A, B, C and D respectively, the opposite terminals of which are connected respectively to the inner conductor of the transmission line, as for example, to conductor l2, as shown in connection with the antenna element 2, and to the shield l5.

Since the impedance between the terminals B of the antenna element is balanced with respect to ground, by reason of the form of the antenna employed, it i necessary that the impedance looking into the end of the transmission line shall also be so balanced. To this end a cylindrical grounded sleeve I6 is provided about the end of the shield I5 and insulated therefrom, this sleeve having a length equal to a quarter of a wave length of the wave at which the system operates and being grounded. The enclosed insulated end I! of the shield I5 forms with the sleeve I6 3, transmission line having a length equal to a quarter of a wave length, which line is short circuited at the point I8. Since the sleeve I6 is grounded, the end I! of the shield I5 within the sleeve oscillates with respect to ground in opposed phase relation with respect to the oscillation at that point on the inner conductor I2, and an impedance balanced with respect to ground appears between the inner conductor I2 and the end of the shield II. Thus, oscillations balanced with respect to ground are supplied across the terminals B of the antenna element 2 and a balanced line impedance is presented by the transmission line to those terminals.

A similar means, including sleeve I6, is provided on each of the transmission lines II, I2, I3, I4 at the end adjacent to the antenna elements.

Additional transmission lines over which reception is had are connected to the diiTerent antenna elements. These transmissoin lines comprise the lines I9, 20. 2| and 22. These lines are likewise provided with sleeves I6 at the end adjacent the antenna element, thereby to present an impedance balanced with respect to ground to the terminals of the respective antenna elements.

These lines I9, 20, 2| and 22 extend from the antenna elements to the respective corners AI, BI, CI and DI of a transmission line loop or, as I shall term it, phasing rectangle. This loop, or phasing rectangle, comprises simply a concentric transmission line arranged in the form of a loop. Preferably the points AI and CI are spaced apart on the loop equally with points BI and DI; and likewise AI and BI are spaced apart equally with points CI and DI.

Additional transmission lines 23, 24, 25 and 26 extend from points midway in the respective sides of the phasing rectangle to a common point 21, and are there joined together and connected through a common line 28 to the receiving equipment.

At certain points KI, K2, K3 and K4, alon the length of these transmission lines 23, 24, 25 and 2B, stub lines 29, 30, 3|, 32 are provided, each leading to a diode 29', 39', 3| and 32' respeotively arranged to become conductive during transmission, thereby. to protect the receiving equipment, as will later be more particularly described.

At these same points KI, K2, K3, and K4 are additional stub lines 33, 34, 35 and 36 each leading to a respective capacitance electrode 31, 38, 39 and 49 of a capacitance switching device 4! which I also will later describe. This switching device is operated to effect the change in orientation in a manner presently to be explained.

Referring now to the operation of the system, it will first be understood that for eiiicient reception of energy from the elements I, 2, 3, 4, through the lines I9,"29, 2I and 22 respectively, it is necessary that the lines I I, I2,.I3 and I4 over which the energy is supplied to the antenna elements shall present high impedance to the respective receiving lines thereby not to constitute a low impedance path in shunt to the receiving 4 line. To this end, each of the lines II, I2, I3, I4 has a length equal to an odd number of quarter wave lengths of the wave at which the system operates, this length being measured from the feedpoints A, B, C, or D of the respective antennae elements to the common point I 9 where these various lines are connected together. This point is connected to the transmitter through the line 9, which has a length equal to an even number of quarter wave lengths. Since the transmitter itself, may present a low impedance to the transmission line 9, that low impedance appears between the conductors of the transmission line at the point Ill because the transmission line 9 has a length equal to an even number of quarter wave lengths. If the impedance of the transmitter is not low the length of line 9 may be chosen to produce low impedance at point I6. Then, since each of the lines II, l2, I3, I4 has a length equal to an odd number of quarter wave lengths it acts as an impedance inversion network and produces a high impedance at the feedpoint A, B, C, or D of the respective antenna elements. Thus, these lines are in effect, not present during reception.

The transmitter 8 is, of course, one adapted for the transmission of impulses in rapid succession, these impulses bein radiated to a remote point and then are again received as a reflection from any remote surface on which they may impinge, the reception occurring during the intervals between the outgoing pulses.

Since all the lines II, i2, I3, I4 supply oscillations in phase to all of the elements I, 2, 3, and 4, these elements radiate together to project a beam of waves at right angles to the plane of the mattress comprising the elements I, 2, 3, and 4.

In the embodiment shown in Fig, 1, this direction of transmission of the impulses may be varied only by varying the physical orientation of the mattress itself. With respect to reception, however, the directivity may be varied by operation of the capacitance switch M. This switch operates to confine reception to only one of the transmission lines 23, 24, 25 and 26 at any time.

This capacitance switch, in addition to the electrodes 31, 38, 39, and 40 comprises a rotor 42, which may have the form of a disk with a ninety degree are removed therefrom so that the disk cooperates with three of the stationary electrodes 31, 38, 39. 40 at one time, thereby to produce large capacity between the disk and the cooperating electrodes, whereas low capacity exists between the disk and the third electrode. Thus, with the disk 42 in the position shown each of the electrodes 37, 38 and 49 are connected to ground at the rotor 42 through high capacitance and hence low impedance. These electrodes are joined by 0 transmission lines 33, 34, and 36 to the points KI,

K2 and K4, which lines have a length equal to an even number of quarterwave lengths of the wave atwhich the system operates. Thus, the transmission lines 23, 24 and 26 are each effectively short-circuited at the points KI, K2, and K4, by the respective transmission lines 33, 34 and 36, while the transmission line 25 is not so short circuited at the point K3 by line 35 because of the high impedance between the electrode 39 and ground. Thus only transmission line 25 is in condition for reception.

Short circuits at the points KI, K2 and K4 on the lines 23, 24 and 26 do not impair reception over the line 25 because these points are so positioned upon the respective lines as to avoid such impairment. That is, the-transmission lines ex tending from the point 21 to the points Kl, K2, K3'and K4 have lengths equal to an odd number of quarter wave lengts of the wave at which the system operates so that a short at any of these points K produces a high impedance at the point 27.

Similarly, each of thelines 23, 24, 25 and 26 has an odd number of quarter wave lengths in length from the respective point TI, T2, E! or E2 to which it is connected and its own K point so that a short circuit at any of the K points produces high impedance at the corresponding point T4, T2, Elor E2. Thus, the line 25 isin condition for reception since it is not short circuited either at point E2, or 21, and since line 35 presents high impedancethereto.

Of course, reception may be had over any one of the lines 23, 24, 25 and 26 by operating the disk 42 of the capacitance switch to the corresponding position.

Let us assume now, again, that the disk 42 is in theposition shown in the drawings and that reception is being had over transmission line 25. This transmission line is connected to the point E2 on the phasing rectangle. This point E2 is, in turn, connected to the antenn elements 3 and 4 through lines of equal length; and similarly the point E2 is connected to the antenna elements I and 2 through lines of equal length. The lines extending from the point E2 to the elements 'I and 2, however, are longer than those extending to the elements 3 and 4. Thus, waves arriving from a direction in the vertical plane above the normal of the mattress and which are intercepted by the antennae l and 2 arrive at the point E2 in phase with waves arriving from the same direction and intercepted by elements 3 and 4. Thus, the maximum directivity of the system is at an angle to the normal of the mattress in the vertical plane although it is normal to the mattress in the horizontal plane. This angle to the normal is, of course, dependent upon the length of the sides of the phasing rectangle since the lines I9, 20, 2| and 22 are preferably of equal length.

Now let us suppose that the disk 42 is rotated in a counter-clockwise direction through ninety degrees, then high capacitance exists between each of electrodes 37, 38 and 39, and ground at the rotor 42, thereby producin a low impedance to ground at the points Kl, K2 and K3 so that the lines 23, 24 and 25 are disabled. Electrode 40 however, has high impedance to ground and so line 25 is in condition for reception. This line extends to the point T2 on the phasing square. The point T2 is equidistant from antenna elements 2 and 4 and also from elements I and 3 but the distance from this point T2 to the elements and 3 is greater than that to the elements 2 and 4. Accordingly, waves arriving in the horizontal plane at an angle to the normal which are intercepted by elements 2 and 4 arrive at the point T2 in aiding phase with waves arriving from the same direction and intercepted by elements I and 3. Thus, the maximum directivity of the system is now in the horizontal plane at an angle to the normal, although it is normal to the mattress in the vertical plane.

Now, ifwe rotate the dish .42. from the position shown through 180 degrees, reception is had over til normal of the mattress in the horizontal plane.

Similarly if we rotate the disk 42 so that electrode 31 has high impedance to ground the reception is over transmission line 23, which extends to the point TI on the phasing rectangle. Maximum directivity isagain normal to the mattress in the vertical plane but at an angle to the normal of the mattress in the horizontal plane, the angle being opposite to that occurrin when reception occurred over the line 26 extending from point T2.

Thus by rotation of the condenser .42, rotation of the directivity of the pattern may be had through the four directions about the normal of the mattress. The condenser 42 may be driven by a motor to vary the directivity of the antenna through the four directions in rapid succession.

The receiving equipment 43 may include means such as cathode ray apparatus for indicating the relative intensity of reception from each of the four directions. In this way the movement of a distant object, such as an airplane, in a limited area toward which the mattress is directed may be observed through electrical scanning of that area by variation of the beam cyclically through the four directions about the normal to the mattress.

Of course, if the intense impulses produced by transmitter 8 and supplied over lines H to l4 were allowed to reach the receiver 43 ove the receiving lines with sufiicient intensity, they might cause impairment of the sensitivity of the receiver during the reception period, or even cause permanent injury thereto. In uses of the equipment in which the received signal is an echo, or reflection of the transmitted impulse from a remote surface, or when the received signal is one transmitted from a remote object in response to reception on that object of a transmitted impulse, the reception occurs between the outgoing impulses and not during the transmission of any outgoing pulse. Thus, during reception the high potentials produced by the associated transmitters are not present. If, however, such high potentials are permitted to reach the receiver dureing transmission of the outgoing pulse, they are likely to impair the sensitivity of the receiver to such an extent that it does not recover its sensitivity in time to effect desired response to the arriving signal.

To avoid such effect the diodes 29' to 32 are employed. The anode of each diode is connected to the K point of its respective transmission line through a stub line 29 to 32, respectively, having a length equal to a half wave length or integral multiple thereof. The cathodes of the diodes are grounded and connected to the shields of the different lines. During transmission of any pulse these diodes become conducting and effectively ground the respective K points through the stub lines 29 to 3,2 or so reduce the impedance at the K point that the intensity of voltage reaching the receiver does not impair reception of the impulse to be received.

Fig. 3 represents a modification of the invention in which both transmission and reception takes place over the line 23, 24, 25 and 26. These lines 23, 24, 2.5 and 26 are joined to ether at the point 21 and extend through a commo transmission line 28 to a transmitter 8. At anoint 48 on the transmission line 28 at .a distance equal to an odd number of quarter wave lengths of the wave at which the system operates from the transmitter 8 is connected a transmission line 44 extending to the receiving equipment 43.

To protect the receiving equipment from the intense impulses produced by the transmitter, the diode 45 is provided connected through a stub transmission line 45 having a length equal to half of a Wave length, or integral multiple'thereof, to a point on the line 44 distant from the point 48 by an amount equal to an odd number of quarter wave lengths. In this way, when high voltages are produced by the transmitter on the inner condoctor of line 28, the diode 45 becomes conductive and produces a low impedance which is effective at the point 41 on the transmission line 44 and thus the diode prevents transmission of the high voltage wave to the receiver. At the same time this low impedance at the point 41', being distant from the line 28 by an amount equal to an odd number of quarter wave lengths;produces a high impedance at the point 43 at which it is connected to the line 28. Thus, this short circuit does not impair transmission over the line 28 and the line 23, 24, 25, or 26 to the antenna.

The directivity of the system is varied in the same way previously described but in this case the direction of maximum effect of the antenna array reception.

A different form of condenser switching mechanism is employed. In this case rotating electrode 42 of the switch cooperates at any one time with only a single one of the stationary electrodes 37, 38, 39 or 43 Thus. in the position shown, all of the electrodes 31, 38 and 40 have high impedance with respect to ground. These different electrodes, however, are connected to the points Kl, K2 and K4 through lines 33, 34 and 33, which have a length equal to an odd number of quarter wave lengths, whereby high impedance at the electrodes 31, 38 and 40 produces low impedance at the points KI, K2 and K4. Thus, three of the lines 23, 24, 25 and 23 are disabled for both transmission and reception.

Low impedance between electrodes 39 and 42, however, produces high impedance at the point K4 and, accordingly, line 25 is in condition. for transmission of energy either for radiation or reception.

Of course, the phasing rectangle operates as previously described, and the direction of its maximum effect is varied through the four directions at angles to the normal of the mattress for both transmission and reception.

Fig. 4 employs a further simplification of the invention in that the phasing rectangle of Figs. 1 and 3 is removed and in. its place is employed what I term as a phasing cross comprising transmission lines 55 and The transmission line 50 connects the feedpoints B and C of the antenna elements 2 and 3 which are arranged at diagonally opposite corners of the rectangle. Similarly, transmission line 51 connects the feedpoints A and D of the elements I' and 4. Points A! and DI on transmission line 5!, preferably equally spaced from the feedpoints A and D, are connected through transmission lines 23 and 25 respectively to the common point 21 and thence through common transmission line 28 to the transmitter. Similarly, points BI and Cl, also preferably equally spaced from the points B and C respectively, are connected through transmission lines 24 and 26 to the point 21 and thence through the common transmission line 28 to the transmitter.

The connection to the receiver is made in the same way as described in connection with Fig. 3.

Points KI, K2, K3, and K4 on these transis varied for both' transmission and mission lines 23, 24,25 and 26 are connected to corresponding electrodes 31, 38, 39 and in the capacitance switching device 4|. In this case the rotor 42 of the switching device is of ashape to cooperate with two-electrodes at any one time, thereby to produce low impedance and high capacitance between the cooperating electrodes and ground. Thus, in the position shown in the drawings, low impedance exists between both elec-v trodes 39 and wand ground Since these electrodes are connected to-the points K3 and K4 respectively on transmission lines 25 and 26 through transmission lines 35 and 36, respectively, which have a length equal to an odd number of quarter wave lengths, high impedance -is produced across the lines 25 and 26 at those points B13 and K4 and thus the lines 25, 26 are in condition for transmission both for radiation and reception. High impedance exists, however, between the electrodes 31 and 38 and ground, which electrodes are connected respectively through lines 33 and 34 to the points KI and K2 on lines 23 and 24 and, again, since the lines 33 and 34 are an odd number of quarter wave lengths in length, low impedance exists across transmission lines 23 and 24 at the points KI and K3 and thus transmission over these lines either during radiation or reception is impaired.

The point Kl is spaced from the point A! on line 23 by a distance equal to an odd number of quarter wave lengths and accordingly transmission over line 55 is not impaired at the point Al. Similarly the point Kl is spaced from the point 2'! by an odd number of quarter wave lengths over line 23 and thus transmission over lines 25 and 26 is not impaired at the point 21. Thus, transmission and reception now takes place over the lines 25 and 25 but not over the lines 23 and 24.

Lines 25 and 26 supply energy in phase to the antenna elements 2 and 4 and they supply enorgy in phase to elements l and 3 but the energy supplied to the elements I and 3 is displaced in phase from the energy supplied to elements 2 and 4 by an amount equal, to the electrical length of the transmission line 53 between points Bi and Ci, which amount'is preferably equal to the distance between the points AI and DI on line 5i. Thus,the direction of maximum effect, both for "radiation and reception by the system is in the horizontal plane at anangle to the normal of the mattress. In the vertical plane, how ever, it lies at the normal of the mattress.

Now by rotation of the switch through its successive positions in clockwise direction, transmission may be made to occur, in the second posi tion of the switch, over the lines 24 and 25; in the third position of the switch over lines 23 and 24, and in the fourth position of the switch over lines 23 and 23. In this way the direction of maximum transmission or reception by the antenna array may be altered about the normal through the four directions in succession.

The form of the invention shown in Fig. 4 possesses certain advantages over the form of the invention shown in Figs. 1 and 3 in that the two lines extendingfrom the respective antennae to the receiver at any one time are free from any cross connections therebetweeri. For example, in Fig. 3; if transmission and reception take place over lin'e26, that line extends to antennae l and 2 over opposite sides of the phasing rectangle including respectively the points El and E2. These two opposite sides, however, are connected togetherby the side including the point TI. While the voltages at the points Al and Cl, during no power flows through the side of the rectangle including point Ti. This side, however, does present reactance at the points Al and Cl. This reactance may readily be shown to be equal to where Z is the surge impedance of the line and its electrical length. While this reactance, in cases where the phase angle between voltages supplied to the different antennae l and 3 is small, and therefore the side is electrically short, is not objectionable, it does to some extent limit the permissible angle between such voltages. For example, if a phase shift of 180 degrees were desired between the antennae i and 3, the side of the rectangle including point Tl would have an electrical length of 180 degrees. As such, the reactance presented thereby at points Al and Cl is zero, or a short circuit. Accordingly, the application of those systems becomes limited to smaller angles and hence to smaller variations of the direction of the maximum effect of the array from the normal.

The system of Fig. 4, however, is free from any such interconnections and is thus capable of wider application and wider variation of the directivity of the antenna array.

In addition, this system of Fig. 4 reduces the amount of transmission line required to be mounted on the antenna mattress. It also, together with the system of Fig. 3, employs only one diode and that need not be mounted on the mat- Z cotangent tress but may be mounted on a fixed part of the equipment near the receiver.

The .form of the invention shown in Fig. 4 is described and claimed in a copending application of Richard C. Longfellow, Serial No. 412,452, entitled Directional radio system and which is assigned to the same assignee as my present application.

While in Figs. 1, 3 and 4 I have shown the radiating elements I, 2, 3 and 4 positioned at the corners of a rectangle, it will be understood that my invention is in no wise limited to such an arrangement since any suitable arrangement may be employed capable of effecting the desired shift in the orientation of the direction of the maximum effect of the radiating system.

In Fig. 5 different antenna elements 83, 84 and 85 are positioned at the vertices of a triangle, each antenna element being connected through a transmission line 88, 81, 88 respectively, to a common point 21 and thence through the line 28 to the transmitter and to the receiver as described in connection with Figs. 3 and 4.,

Lines 88, 81 and 88 are interconnected by lines 89, 9D, and 98' so that energy supplied over any one of the transmission lines 86, 81, and 88 is supplied to all of the radiating elements 83, 84 and 85.

Points on each of lines 88, 81, and 88 spaced from the point 21 by an odd number of quarter wave lengths of the wave at which the system operates, and also spaced from the lines 89, 98, and 90' by an odd number of quarter wave lengths, are connected through transmission lines 9|, 92 and 93 to the electrodes of the capacitance switch 94. These lines 9!, 92 and 93 have a length equal to an odd multiple of a quarter of a wave length.

The electrodes 95, 98 and 91 of the capacitance switch are spaced apart around a circumference by 120 degrees and the rotor 98 of the condenser tion with the rotor.

10 comprises a segment having an angular width of approximately 1.20 degrees.

In the position shown, the rotor 98 is in high capacitance relationship with the fixed electrode 89 and in low capacitance relationship with electrodes and 91. This means that lines 88 and 88 are disabled by the low impedance produced thereon 'by the lines 9| and 93, whereas the line 81 is in transmitting condition. This line transmits energy to all of the radiating elements 83, 84 and 85 but the distances over the respective conductors to the difierent elements are such as to throw the beam at an angle to the normal of the antenna mattress. If the rotor 98 of the switch 94 be rotated to one of its other positions, then energy is supplied over the lines 8 8, or 88, to all of the antenna elements and these radiators would be energized in proper phase to throw the beam at the same angle from'the normal but in a plan with the normal spaced approximately degrees away from the plane in which it was first projected. Thus, by rotation of the switch, the direction of maximum efiect of the combined mattress may be rotated through directions spaced from th normal of the mattress by a predetermined angle in each of three difierent equally spaced planes.

If desired, six antennae elements may be employedand located at the vertices of a six-sided polygon but ordinarily a lower number of "antennae elements is to be preferred.

Figs. 6 and '7 illustrate in plan and in elevation, the-capacitance switch of the type shown in Fig. 1. The different stationary electrodes of the switch are indicated at 31, 38, 39 and 88 equally spaced about a circumference, the center of which is the center of the rotating electrode M. The rotor electrode is shown as mounted upon the shaft of a motor-68 through which the rotor ii may be grounded. The shape of this rotor is best shown by the dotted line in Fig. 6 although the top portion of the casing is shown as broken away at 8| to indicate the shape of the rotor at 82 by full lines. It will be seen that it comprises five arcuate or fan-shaped sections 82, separated by open spaces 83, 64, 65, 86 and 81 so spaced about the periphery of the rotor that one of the stationary electrodes is substantially always uncovered by the rotor, while all of the otherstationary electrodes are covered. Thus with the rotor in the position shown in Fig. 6 the electrode 38 is in non-cooperating, or in low capacitance relation with the rotor, while electrodes 31, 39 and 48 are all completely covered by the rotor and hence in high capacitance relation thereto.

Now, {if the rotor be rotated through a distance corresponding to a third of the angular width of one ofthe segments in the clockwise direction, electrode 39 is completely uncovered and in low capacitance relation with the rotor, whereas electrodes 31,38 and 48 are in high capacitance rela- Upon further rotation by another equal distance, electrode 48 is uncovered; and'thus each of the diiferent electrodes are 'uncovered and in low capacitance relationship with the rotor in succession.

Fig. 8 shows the structure of the condenser switching device employed in the equipment of Fig. '4 in which the rotor 42 comprises a semicircular disk arranged to cooperate at any time with .two of the electrodes 31, 38, 39 and 40. This mechanism .ishoused within a housing 88 to whichthe outer shield conductors of the different transmission lines 33, 34, 35 and 36 are connected.

. Fi'g. 9 showsthe structure of the diodes employed in all of the different figures. This diode comprises an anode 15] having a screw threaded projection ll at the top thereof which may be screwed into the end of the inner conductor 12 of any transmission line to which the anode is to be connected. The outer conductor of the transmission line is shown at 13 as having a flange '14 about the end thereof which may be attached to a plate 15 but insulated therefrom by means of insulation 16. The cathode ll of the diode which may be indirectly heated by means of a filament 18, is mounted upon the plate '55 and a glass seal 80 is arranged between the anode and the plate whereby the interior space within the seal and between the cathode and anode may be evacuated. The cathode may be heated by means of alternating current supplied through a transformer M to the heater it. Thus, whenever high potential is impressed upon the inner conductor 72 of the transmission line, as during the radiation of impulses produced by the transmitter, the diode becomes conducting and produces a low impedance between the anode and the end of the conductor 32' and ground. Preferably a source of potential 32 is connected between the flange 74 and the plate 35 therebyto render the anode of the diode slightly negative with respect to the cathode thereby to prevent the normal fiow of current to the anode due to thermal agitation and the like. I V

The connection for direct current between the outer conductor 13 and the inner conductor 12 of the transmisison line is effected through connections within the transmitting and receiving apparatus.

In the descriptions of the different systems illustrated, I have referred to lines an odd 'multiple of a quarter wave length in length. It will, of course, be understood that I include the multiple one since very commonly such lines may be of a single quarter wave length in length.

In connection with the capacitance switching device which I have mentioned and described, I have referred to it as having large capacitance between certain electrodes at one time and low capacitance between the same electrodes at another time dependent upon the position of the electrode thereof, this electrode being movable to cooperate with dfferent stationary electrodes. Thus, the device acts as a switching device having closed circuit and open circuit positions.

The effect of this switching device may be improved by adjustment thereof, and by adjustment of the lines through which it operates, to change such lines from the quarter wave length mode of action when the rotor of the switch is in one position to a half wave length mode of action when the rotor of the switch is in a diiferent position.

Referring, for example, to the form of the in- I vent'ion shown in Fig. 4 in which the lines 33, 34,

35 and 35 are described as of a quarter of a wave length in length, or odd multiple thereof, if desired, these lines may be made of a length different from a quarter of a wave length or any multiple thereof if the capacitance between the electrodes 31, 38, 39 and 49 and ground be so adjusted, that when the rotor is in the position shown, lines 35 and 35 including the capacitance between ground and the respective electrodes 39 and 48 be of a half wave length in length, and lines 33 and 34, including the capacitance between ground and the respective electrodes 31 and 38 be adjusted to be of a quarter wave length in length. Thus, lines 35 and 3t amount to open cirtheme 12 cuits at the pointsK3 and K4 whereas lines 33 and 34 amount to short circuits at the points KI and K2 and the overall action is as previously described. This adjustment may require additional adjustable, or trimmer, electrodes within the capacitance device thereby to provide proper values of the capacitance to produce the quarter wave and half wave modes of action but the improved effect of the switching device well warrants the provision of such additional electrodes. Of course, to produce the half wave mode of operation some inductance within the switching device is required. This inductance is present in the path through the rotor and motor shaft of the condenser to ground, which elements may be proportioned relative to capacitance between any stationary electrode and ground to produce the desired half wave mode of action. Preferably the lines 33, 34, 35 and 36, for such operation may have an electrical length, of themselves, equal to an eighth of a wave length, or equal to an eighth of a wave length plus a half wave length or multiple thereof. This type of action of the switching device may be employed in connection with any of the systems described.

This adjustment and action of the switching device is better described and is claimed in copending application of Franklin G. Patterson, filed December 1, 1941, having Serial No. 421,126, entitled Transmission systems, and which is assigned to the same assignee as mypresent application.

While I have shown particular embodiments of my invention, it will, of course, be understood that I do not wish to be limited thereto since various modifications both in the circuit arrangement and in the instrumentalities employed may be made and I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A directive radio apparatus having maximum directivity in any of at least three different directions, said apparatus comprising a plurality of antenna elements arranged in a common plane at the vertices of a polygon, transmission lines extending between different of said antenna elements and having a plurality of points thereon at each of which waves from a corresponding one of said directions at an angle to the normal of said plane intercepted by different of said antenna elements arrive in phase, lines extending from each of said points, and means selectively to receive energy over any of said lines in accordance with the direction from which reception is desired.

2. In means to receive radio waves from any of a plurality of directions lying in respective planes radiating from a common line, the combination of a plurality of antenna elements arranged at the vertices of a polygon at right angles to said line, transmission lines extending between different of said antenna elements, receiving apparatus, connections corresponding to said different directions extending from said receiving apparatus to respective points on said lines, said lines being so arranged that energy received from any of said directions intercepted by different of said antenna elements arrives at a corresponding one of said points in phase, and meansselectively to interrupt reception over certain ofsaid connections while maintaining reception over another of said connections whereby energy may be selectively received from any of said directions to the exclusion of the other directions.

3. In a radio system having variable directiv ity, means to change the direction of maximum eiiect of said system to directions in any or at least three different planes radiating at predetermined angles from a common line, a plurality of antenna elements arranged at the vertices of a polygon at right angles to said line, transmission lines extending between different of said elements, radio apparatus, connections from said apparatus to dinerent points on said lines, said lines being so arranged that each of said points is unequally spaced thereon from difierent antenna elements, and means to interrupt transmission through any of said connections while maintaining transmission through another of said connections.

4. In a radio system having variable directivity, means to change the direction of maximum effect of said system to any of at least three different planes radiating at right angles from a common line, a plurality of antenna elements arranged at the corners of a polygon at right angles to said line, transmission lines extending between different of said elements, radio apparatus, connections from said apparatus to different points on said lines, said lines being so arranged that each of said points is unequally spaced from different of said antenna elements, and means selectively to roduce a short circuit on any of said connections at a distance from the corresponding one of said points equal to a quarter of a wave length, or odd multiple thereof, of the wave at which said system operates.

5. In a radio-system having variable directivity, means to change the direction of maximum efiect of said system to directions in any one of a number of different planes greater than two radiating at right angles from a common line, a pluralityof antenna elements arranged at the corners of a rectangle at right angles to said line, transmission lines extending between different of said elements, connections corresponding to said different directions extending from respective points on said lines to a common point and thence through a common transmission line to a radio apparatus, said first-mentioned transmission lines being so arranged that each of said first-mentioned points is unequally spaced from difierent antenna elements, and means to produce a low impedance on each connection at a distance from the respective one of said points on said transmission line and from said common transmission line that all of said transmission lines remain in transmitting condition, while transmission through said connection on which the low impedance is produced is impaired by said low impedance.

6. In combination, a plurality of antenna elements arranged at the corners of a polygon, a transmission line loop, connections from differentantenna elements to correspondingly spaced points on said loop, radio apparatus, and connections from said apparatus to points on said loop intermediate said first mentioned points.

7. In combination, a plurality of antenna elements arranged at the vertices of a polygon, a transmission'line loop, transmission lines of equal length extending from the respective antenna elements to points positioned about said loop in accordance with the relative spacing of the different antenna elements, radio apparatus, and means to establish transmission between said apparatus and any one of those points on the loop which are midway between adjacent of said first mentioned points.

8-. In combination, 'a plurality of antenna 'ele' ments arranged at the corners of a. rectangle, a transmission line loop, lines of equallength extending from each antenna element to corresponding points on said loop, said corresponding points being spaced about said loop such that energy intercepted by any adjacent pair of said antenna elements arrives at a certain point on the loop in phase with energy from the same direction intercepted by the other pair of antenna elements, whereby four of said certain points are produced on said loops at which energy from respective directions intercepted by all of said antenna elements arrive in phase.

9. In combination, a plurality of antenna elements arranged at the corners of a rectangle, a transmission line loop, lines of equal length extending from each antenna element to corresponding points on said loop, said corresponding points being spaced about said loop in such a way that four points are produced on the loop, each of which are equidistant from the different antenna elements of each pair of adjacent antenna elements.

10. In combination, a plurality of antenna elements arranged at the corners of a rectangle, a transmission line loop, lines of equal length extending from each antenna element tocorresponding points on said loop, said corresponding points being spaced about said loop in such away that four points are produced on the loop each of which are equidistant from the difierent antenna elements of each pair of adjacent antenna elements, permanent connections from each of said four points to radio apparatus and means to interrupt transmission through any of said connections while maintaining transmission through other of said connections thereby to alter the combined directivity of said antenna elements.

11. In combination, a plurality of antenna elements cooperating to produce directivity in different directions, a radio apparatus, transmission line connections extending from each of said antennae to said radio apparatus, said lines being interconnected at both ends the interconnection at the antennae ends being such that the combined directivity of said antennae is variable dependent upon the transmission line connection through which transmission between said difierent antennae and said apparatus occurs, a plurality 0f capacitances, each capacitance being connected across a corresponding one of said lines at a point such that a low impedance thereat impairs transmission through the respective line without impairing transmission through an other line, and means to vary said capacitances.

12. In combination, a plurality of antenna elements positioned in an arrayto produce maximum efiect of said array with respect to certain directions, radio apparatus, a plurality of transmission lines extending from said antennae to said apparatus, and an interconnection between said lines so arranged that a path exists from all of said antennae over any one of said lines having a length such that the array has maximum effect in a direction corresponding to the line over which transmission occurs, and means to change the line through which transmission occurs to change the direction of maximum effect of said array.

13. In combination, a plurality of antenna elements positioned in an array to produce maximum efiect of said array with respect to certain directions, radio apparatus, a plurality of transmission lines extending from said antennae to 15 16 said apparatus, and an interconnection between antennae through any one of said lines are of said lines whereby energy is transmitted between lengths to produce maximum effect in a direcsaid apparatus and all of said antennae over any tion corresponding to the line included in said one of said lines, and means to select any one of paths. said lines, said interconnection being so arranged 5 LAURANCE M. LEEDS.

that the paths between the apparatus and said 

